# Lesson 15

# Functions Lesson. In this lesson,
# you will learn how to define and
# use functions in Sonic Pi.

# General Instructions:
#
# This lesson contains one example and
# one exercise (A).
#
# To listen to an example, change "comment"
# to "uncomment" on the "comment do" line,
# then click the "Run" menu command at the
# top of the Sonic Pi editor window.
# When you are done with the example, turn
# it off by changing "uncomment" back to
# "comment," and move on to the next section
# of the lesson.
#

# You may have noticed that creating
# interesting musical patterns in Sonic
# Pi might involve writing repetitive
# lines of code. You can "package" a
# block of code by defining it as a function.

# Example 1: Musical Functions.

comment do
  define :twinkle_a do
    melody_a = [:C4, :C4, :G4, :G4,
                :A4, :A4, :G4]
    index = 0
    count = melody_a.length
    count.times do
      play melody_a[index]
      sleep 1
      index += 1
    end
    sleep 1
  end
  define :twinkle_b do
    melody_b = [:F4, :F4, :E4, :E4,
                :D4, :D4, :C4]
    index = 0
    count = melody_b.length
    count.times do
      play melody_b[index]
      sleep 1
      index += 1
    end
    sleep 1
  end
  define :twinkle_c do
    melody_c = [:G4, :G4, :F4, :F4,
                :E4, :E4, :D4]
    index = 0
    count = melody_c.length
    count.times do
      play melody_c[index]
      sleep 1
      index += 1
    end
    sleep 1
  end

  use_bpm 120
  twinkle_a
  twinkle_b
  twinkle_c
  twinkle_c
  twinkle_a
  twinkle_b

end

# Exercise A:
# Define a new function named "twinkle_play"
# that wraps the calls to twinkle_a,
# twinkle_b, and twinkle_c in a single function.
# Call twinkle_play from inside a
# thread, and then call it outside (below)
# the thread after a delay of four beats. Then
# do a version with a delay of eight beats.